Cisco IOS XR through 4.3.2 on Gigabit Switch Router (GSR) 12000 devices does not properly check for a Bidirectional Forwarding Detection (BFD) header in a UDP packet, which allows remote attackers to cause a denial of service (line-card restart) via a crafted packet, aka Bug ID CSCuw56900.
http://www.securitytracker.com/id/1035314
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160311-gsr